BD Vacutainer serum tubes with Thrombin additive are used for stat chemistry determinations Serum tubes are coated with silicone and micronized silica particles to accelerate clotting; silicone coating on the walls of most serum tubes reduces adherence of red cells to tube walls Blood is drawn directly from the vein into the evacuated sterile collection tubes Only one venipuncture is needed to draw multiple samples Tubes can be changed while needle and plastic holder remain in place on patient's arm Closures are color coded Hemogard™ Closures Safety shield designed for safer tube handling Rubber stopper is recessed inside the plastic shield, so any drops left by a blood collection needle remain isolated from potential contact Shield is designed to protect lab personnel from direct contact with blood on the stopper or around the outer rim of the tube, as well as from blood splattering upon opening the tube